Method for simulating the functional attributes of human milk oligosaccharides in formula-fed infants

ABSTRACT

The present invention is directed to a novel method for increasing the production of acetate, decreasing the production of butyrate, increasing the population and species of beneficial bacteria and slowing the rate of fermentation of prebiotics within the gut of a formula-fed infant. The method comprises administration of a therapeutically effective amount of PDX to the infant.

This application is a continuation of commonly assigned U.S. patent application Ser. No. 11/172,123, filed Jun. 30, 2005 now U.S. Pat. No. 7,572,474, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a method for simulating the functional attributes of human milk oligosaccharides in infants.

(2) Description of the Related Art

The infant gut microflora is rapidly established in the first few weeks following birth. The nature of this intestinal colonization is initially determined by early exposure to environmental sources of microbes as well as the health of the infant. Whether the infant is breast-fed or formula fed also has a strong influence on the intestinal bacterial population.

In the breast-fed infant, for example, Bifidobacterium spp. dominate among intestinal bacteria, with Streptococcus spp. and Lactobacillus spp. as less common contributors. In contrast, the microflora of formula-fed infants is more diverse, containing Bifidobacterium spp. and Bacteroides spp. as well as the more pathogenic species, Staphylococcus, Escherichia coli and Clostridia. The varied species of Bifidobacterium in the stools of breast-fed and formula-fed infants differ as well.

Bifidobacteria are generally considered “beneficial” bacteria and are known to protect against colonization by pathogenic bacteria. This likely occurs through competition for cell surface receptors, competition for essential nutrients, production of anti-microbial agents, and production of inhibitory compounds such as short chain fatty acids (SCFA) which may decrease fecal pH and inhibit potentially pathogenic bacteria. Bifidobacteria are also associated with resistance to gastrointestinal (GI) tract and respiratory infection as well as an enhanced immune function in children and infants. Therefore, the promotion of an intestinal environment in which Bifidobacteria dominate has become a goal in the development of nutritional formulations for formula-fed infants.

Human milk (HM) contains a number of factors that may contribute to the growth and population of Bifidobacteria in the gut microflora of infants. Among these factors is a complex mixture of more than 130 different oligosaccharides that reach levels as high as 8-12 g/L in transitional and mature milk. Kunz, et al., Oligosaccharides in Human Milk: Structure, Functional, and Metabolic Aspects, Ann. Rev. Nutr. 20: 699-722 (2000). These oligosaccharides are resistant to enzymatic digestion in the upper gastrointestinal tract and reach the colon intact, where they serve as substrates for colonic fermentation.

HM oligosaccharides are believed to elicit an increase in the number of Bifidobacteria in the colonic flora, along with a reduction in the number of potentially pathogenic bacteria. Kunz, et al., Oligosaccharides in Human Milk: Structure, Functional, and Metabolic Aspects, Ann. Rev. Nutr. 20: 699-722 (2000); Newburg, Do the Binding Properties of Oligosaccharides in Milk Protect Human Infants from Gastrointestinal Bacteria?, J. Nutr. 217:S980-S984 (1997). One way that HM oligosaccharides may increase the number of Bifidobacteria and reduce the number of potentially pathogenic bacteria is by acting as competitive receptors and inhibiting the binding of pathogens to the cell surface. Rivero-Urgell, et al., Oligosaccharides: Application in Infant Food, Early Hum. Dev. 65(S):43-52 (2001).

In addition to reducing the number of pathogenic bacteria and promoting the population of bifidobacteria, when HM oligosaccharides are fermented, they produce SCFAs such as acetic, propionic and butyric acids. These SCFAs are believed to contribute to caloric content, serve as a major energy source for the intestinal epithelium, stimulate sodium and water absorption in the colon, and enhance small bowel digestion and absorption. In addition, SCFA are believed to contribute to overall gastrointestinal health by modulating gastrointestinal development and immune function.

The fermentation of HM oligosaccharides also reduces fecal ammonia, amine, and phenol concentrations, which have been implicated as the major odorous components of feces. Cummings & Macfarlane, The Control and Consequences of Bacterial Fermentation in the Human Colon, J. Appl. Bacteriol. 70:443-459 (1991); Miner & Hazen, Ammonia and Amines: Components of Swine-Building Odor ASAE 12:772-774 (1969); Spoelstra, Origin of Objectionable Components in Piggery Wastes and the Possibility of Applying Indicator Components for Studying Odour Development, Agric. Environ. 5:241-260 (1980); O'Neill & Phillips, A Review of the Control of Odor Nuisance from Livestock Buildings: Part 3. Properties of the Odorous Substances which have been Identified in Livestock Wastes or in the Air Around them J. Agric. Eng. Res. 53:23-50 (1992).

As a result of the oligosaccharides present in HM, the SCFA profile of a breast-fed infant is very different from that of a formula-fed infant. For example, breast-fed infants produce virtually no butyrate, with acetate comprising approximately 96% of the total SCFA production. Lifschitz, et al., Characterization of Carbohydrate Fermentation in Feces of Formula-Fed and Breast-Fed Infants, Pediatr. Res. 27:165-169 (1990); Siigur, et al., Faecal Short-Chain Fatty Acids in Breast-Fed and Bottle-Fed Infants. Acta. Paediatr. 82:536-538 (1993); Edwards, et al., Faecal Short-Chain Fatty Acids in Breast-Fed and Formula-Fed Babies, Acta. Paediatr. 72:459-462 (1994); Parrett & Edwards, In Vitro Fermentation of Carbohydrates by Breast Fed and Formula Fed Infants, Arch. Dis. Child 76:249-253 (1997). In contrast, while formula-fed infants also have acetate (74%) as the major SCFA in feces, they have considerable amounts of propionate (23%) and small amounts of butyrate (3%) present as well. These differences between the SCFA profiles of breast-fed infants and formula-fed infants could affect the energy, digestion, and overall health of the formula-fed infant.

Because cow's milk and commercially available infant formulas that are based on cow's milk provide only trace amounts of oligosaccharides, prebiotics are often used to supplement the diet of formula-fed infants. Prebiotics have been defined as “non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon that can improve the health of the host”. Gibson, G. R. & Roberfroid, M. B., Dietary Modulation of the Human Colonic Microbiota-Introducing the Concept of Probiotics, J. Nutr. 125:1401-1412 (1995). Common prebiotics include fructo-oligosaccharide, gluco-oligosaccharide, galacto-oligosaccharide, isomalto-oligosaccharide, xylo-oligosaccharide and lactulose.

The incorporation of various prebiotic ingredients into infant formulas has been disclosed. For example, U.S. Patent App. No. 20030072865 to Bindels, et al. discloses an infant formula with an improved protein content and at least one prebiotic. The prebiotic component can be lacto-N-tetaose, lacto-N-fuco-pentaose, lactulose (LOS), lactosucrose, raffinose, galacto-oligosaccharide (GOS), fructo-oligosaccharide (FOS), oligosaccharides derived from soybean polysaccharides, mannose-based oligosaccharides, arabino-oligosaccharides, xylo-oligosaccharides, isomalto-oligo-saccharides, glucans, sialyl oligosaccharides, and fuco-oligosaccharides.

Similarly, U.S. Patent App. No. 20040191234 to Haschke discloses a method for enhancing the immune response which comprises administering at least one prebiotic. The prebiotic can be an oligosaccharide produced from glucose, galactose, xylose, maltose, sucrose, lactose, starch, xylan, hemicellulose, inulin, or a mixture thereof. The prebiotic can be present in an infant cereal.

Unfortunately, however, there are many disadvantages in the administration of the above prebiotics to formula-fed infants. While they may beneficially affect the population of probiotics in the gut, they do not produce a SCFA profile that is similar to that of a breast-fed infant. Additionally, the fermentation of many of these prebiotic substances occurs at a very rapid rate, which often produces excess gas, abdominal distension, bloating, and diarrhea. Therefore, the choice of prebiotic substances in infant formulas should be made with the goal of maximizing potential benefits and minimizing such unwanted side-effects.

Accordingly, it would be beneficial to provide a prebiotic substance that simulates the functional attributes of human milk oligosaccharides in infants, such as an increase in the population and species of beneficial bacteria in the infant gut and production of a SCFA profile similar to that of a breast-fed infant. Additionally, the prebiotic substance should be well tolerated in infants and should not produce or cause excess gas, abdominal distension, bloating or diarrhea.

SUMMARY OF THE INVENTION

Briefly, therefore, the present invention is directed to a novel method for simulating the functional attributes of human milk oligosaccharides in a formula-fed infant, the method comprising administering a therapeutically effective amount of polydextrose (PDX) to the infant.

The present invention is also directed to a novel method for increasing the population and species of beneficial bacteria in a formula-fed infant, the method comprising administering a therapeutically effective amount of PDX to the infant.

In another aspect, the present invention is directed to a novel method for producing a short-chain fatty acid (SCFA) profile in a formula-fed infant which is similar to that of a breast-fed infant, the method comprising administering a therapeutically effective amount of PDX to the infant. Specifically, PDX can cause the SCFA profile to have an increased level of acetate and a decrease in butyrate.

In yet another aspect, the present invention is directed to a novel method for decreasing the rate and extent of fermentation of prebiotics within the gut of a formula-fed infant, the method comprising administering a therapeutically effective amount of PDX to the infant. More particularly, the invention reduces the total gas production as well as the carbon dioxide production within the infant gut.

Among the several advantages found to be achieved by the present invention, it is well tolerated in infants and simulates the functional attributes of human milk oligosaccharides in infants, such as an increased population and species of beneficial bacteria in the infant gut, optimization of stool characteristics, and production of a SCFA profile similar to that of a breast-fed infant.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings.

FIG. 1 illustrates total SCFA production during the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 2 illustrates pH changes during the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 3 illustrates the relative proportion of acetic acid production in the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 4 illustrates the relative proportion of propionic acid production in the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 5 illustrates the relative proportion of butyric acid production in the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 6 illustrates the relative proportions of acetic acid, propionic acid, butyric acid and total SCFA production in the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 7 illustrates the total SCFA production during the fermentation of various combinations of prebiotic carbohydrates.

FIG. 8 illustrates the pH changes during the fermentation of various combinations of prebiotic carbohydrates.

FIG. 9 illustrates the total SCFA production during the fermentation of different combinations of PDX and GOS.

FIG. 10 illustrates the concentration of acetic acid produced during the fermentation of different combinations of PDX and GOS.

FIG. 11 illustrates the concentrations of propionic acid produced during the fermentation of different combinations of PDX and GOS.

FIG. 12 illustrates the concentration of butyric acid produced during the fermentation of different combinations of PDX and GOS.

FIG. 13 illustrates the formation of gases as total volume during the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 14 illustrates the formation gases as carbon dioxide concentration during the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 15 illustrates the formation of gases as hydrogen concentration during the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 16 illustrates the formation of gases as hydrogen disulphide concentration during the fermentation of GOS, LOS, PDX2 and FOS.

FIG. 17 is a summary of the prebiotic effect of human milk, FOS, LOS, GOS, PDX, and various combinations thereof on fecal microflora.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference now will be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not a limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment.

Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present invention are disclosed in or are obvious from the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.

DEFINITIONS

As used herein, the term “prebiotic” means a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon that can improve the health of the host.

The term “probiotic” means a microorganism with low or no pathogenicity that exerts beneficial effects on the health of the host.

As used herein, the term “infant” means a human that is less than about one year old.

A “therapeutically effective amount”, as used in the present application, means an amount that provides a prebiotic effect in the subject.

The term “simulating”, as used herein means having or taking the form or appearance of or having or producing a symptomatic resemblance to.

The terms “functional attributes” mean any inherent quality or characteristic that causes something to occur. Examples of functional attributes of human milk oligosaccharides in the present invention can include the increase of the population and species of beneficial bacteria, production of a SCFA profile that is high in acetic acid and low in butyric acid, and production of a slow rate and low extent of fermentation of prebiotics in the gut.

As used herein, the term “infant formula” means a composition that satisfies the nutrient requirements of an infant by being a substitute for human milk. In the United States, the content of an infant formula is dictated by the federal regulations set forth at 21 C.F.R. Sections 100, 106, and 107. These regulations define macronutrient, vitamin, mineral, and other ingredient levels in an effort to stimulate the nutritional and other properties of human breast milk.

INVENTION

In accordance with the present invention, a novel method for simulating the functional attributes of human milk oligosaccharides in formula-fed infants has been discovered. The method involves providing a therapeutically effective amount of PDX to the infant. The administration of PDX provides a beneficial effect on the population and species of probiotics, produces a SCFA profile that is similar to that of breast-fed infants and is physically well-tolerated by infants.

PDX is a non-digestible carbohydrate that has been synthesized from randomly cross-linked glucose and sorbitol. It is not digested in the upper GI tract and is only partially fermented in the lower GI tract, making it a beneficial ingredient for digestive health. The physiological benefits of PDX include increased fecal bulk, reduced transit time, lower fecal pH and reduced concentration of putrefactive substances in the colon. In adults, PDX ingestion has also been shown to aid in the promotion and growth of beneficial bacteria in the intestine and production of SCFAs.

PDX has been identified as a prebiotic substance for adults based on its functions in the GI tract. For example, U.S. Patent App. No. 20040062758 to Mayra-Makinen, et al. relates to a composition which comprises a probiotic and one or more prebiotics, where the prebiotic can be GOS, palatinoseoligosaccharide, soybean oligosaccharide, gentiooligosaccharide, xylooligomers, nondegradable starch, lactosaccharose, LOS, lactitol, maltitol, or PDX. Similarly, U.S. Pat. No. 4,859,488 to Kan relates to a liquid food comprising PDX and oligosaccharides that is useful for curing constipation.

PDX has not, however, been identified as a prebiotic that provides the benefits of the present invention and can be administered to infants. The gut microflora of infants is well known to be far less developed than that of an adult. While the microflora of the adult human consists of more than 10¹³ microorganisms and nearly 500 species, the gut microflora of an infant contains only a fraction of those microorganisms, both in absolute number and in species diversity. Because the bacterial populations and species vary so immensely between the gut of an infant and an adult, it cannot be assumed that a prebiotic substance that has a beneficial effect on adults would also have a beneficial effect on infants.

In adults, PDX ingestion has been shown to increase the production of acetate and butyrate. Because butyrate is not noted in appreciable levels in breast-fed infants and has been associated with harmful effects if produced at significant levels in the infant intestine, PDX would not generally be considered appropriate for infant nutrition based on its observed effects in the adult GI system. Thus, it was surprising and unexpected that PDX was actually metabolized primarily to acetate and propionate, with little butyrate formation. Thus, not only did PDX have a positive impact on the population and species of beneficial bacteria in the infant intestinal tract, but PDX also created a SCFA profile that was very similar to that of a breast-fed infant and would be extremely well-tolerated by infants.

One particular reference that relates to PDX in the context of infant administration actually teaches the converse of the present invention. In U.S. Patent App. No. 20030157146 to Rautonen, it is asserted that PDX can stimulate the immune system of infants. In that application, however, the Applicant discloses that PDX actually decreased the population of Bifidobacteria in the infant gut (Rautonen App., para. 0074). Applicant justifies this result by noting that “an abundance of bifidobacteria may cause also less desirable physiological effects such as enteric bacterial diseases and immunosuppression.” (Rautonen App., para. 0069).

Because the reference teaches that PDX actually decreases the population of Bifidobacteria in the infant gut, it is in direct conflict with the teaching of the present application. Additionally, the reference does not demonstrate that PDX increases the production of acetate, decreases the production of butyrate or decreases the rate of fermentation of prebiotics within the infant gut.

In the method of the present invention, a therapeutically effective amount of PDX is administered to an infant for the purpose of simulating the functional attributes of human milk oligosaccharides. A therapeutically effective amount of PDX may be between about 1.0 g/L and 10.0 g/L, administered daily. In another embodiment, a therapeutically effective amount of PDX may be between 2.0 g/L and 8.0 g/L, administered daily.

PDX is commercially available from a variety of sources. For example, STA-LITE® PDX is available in 5 lb bags from Honeyville Grain, Inc., located in Salt lake City, Utah. Alternatively, Litesse® Ultra™ PDX is commercially available from Danisco Sweeteners, Ltd., located in the United Kingdom.

PDX is well-suited for incorporation into an infant formula, as it contains only 1 Cal/g, as compared to 4 Cal/g for typical prebiotics. It is also highly soluble and neutral tasting. Therefore, its addition to infant formula would not change the physical or taste characteristics of the composition.

The form of administration of PDX in the method of the invention is not critical, as long as a therapeutically effective amount is administered. Most conveniently, the PDX is supplemented into infant formula which is then fed to an infant.

The infant formula for use in the present invention is preferably nutritionally complete and typically contains suitable types and amounts of lipid, carbohydrate, protein, vitamins and minerals. The amount of lipid or fat typically can vary from about 3 to about 7 g/100 kcal. The amount of protein typically can vary from about 1 to about 5 g/100 kcal. The amount of carbohydrate typically can vary from about 8 to about 12 g/100 kcal. Protein sources can be any used in the art, e.g., nonfat milk, whey protein, casein, casein protein, soy protein, hydrolyzed protein, amino acids, and the like. Carbohydrate sources can be any used in the art, e.g., lactose, glucose, corn syrup solids, maltodextrins, sucrose, starch, rice syrup solids, and the like. Lipid sources can be any used in the art, e.g., vegetable oils such as palm oil, soybean oil, palmolein, coconut oil, medium chain triglyceride oil, high oleic sunflower oil, high oleic safflower oil, and the like.

Conveniently, commercially available infant formula can be used. For example, Enfalac, Enfamil®, Enfamil® Premature Formula, Enfamil® with Iron, Lactofree®, Nutramigen®, Pregestimil®, or ProSobee® (available from Mead Johnson & Company, Evansville, Ind., U.S.A.) may be supplemented with suitable levels of PDX and used in practice of the method of the invention.

In an embodiment of the present invention, PDX can be administered in combination with another prebiotic. The prebiotic selected can be any prebiotic known in the art. Examples of prebiotics include, but are not limited to: FOS, inulin, gluco-oligosaccharide, GOS, isomalto-oligosaccharide, xylo-oligosaccharide, soybean oligosaccharides, chito-oligosaccharide, gentio-oligosaccharide, manno-oligosacchaide, LOS, lactosucrose, raffinose, aribino-oligosaccharide, glucans, siallyl-oligosaccharide, and fuco-oligosaccharide.

In a particular embodiment of the present invention, PDX is administered in combination with GOS. GOS is a mixture of oligosaccharides consisting of D-glucose and D-galactose. It is sometimes referred to as trans-galacto-oligosaccharide. It is produced from D-lactose by β-galactosidase, which can be obtained from Aspergillus oryzae. GOS has been suggested to increase calcium absorption and prevention of bone loss in adults. GOS has been identified as a prebiotic that is useful for administration to infants in U.S. Patent App. No. 20030072865 to Bindels, et al.

In this embodiment, PDX and GOS can be administered in a ratio of PDX:GOS of between about 9:1 and 1:9. In another embodiment, the ratio of PDX:GOS can be between about 5:1 and 1:5. In yet another embodiment, the ratio of PDX:GOS can be between about 1:3 and 3:1. In a particular embodiment, the ratio of PDX to GOS can be about 5:5. In another particular embodiment, the ratio of PDX to GOS can be about 8:2.

A therapeutically effective amount of the PDX:GOS combination may be between about 1.0 g/L and 10.0 g/L, administered daily. In another embodiment, a therapeutically effective amount of the PDX:GOS combination may be between about 2.0 g/L and 8.0 g/L, administered daily. In a particular embodiment, a therapeutically effective amount of the PDX:GOS combination may be about 2 g/L of PDX and 2 g/L of GOS, administered daily.

In another specific embodiment of the present invention, PDX is administered in combination with LOS. LOS is a semisynthetic disaccharide formed from D-galactose and D-fructose and joined by a β-glucosidic linkage. It is resistant to hydrolysis by human digestive enzymes, but is fermented in the small intestine. It is highly soluble and has a sweet taste. LOS has been identified as a prebiotic that is useful for administration to infants in U.S. Patent App. No. 20030072865 to Bindels, et al. LOS is commercially available from a variety of sources.

In this embodiment, PDX and LOS can be administered in a ratio of between about 9:1 and 1:9. In another embodiment, the ratio of PDX to LOS can be between about 5:1 and 1:5. In yet another embodiment, the ratio of PDX to LOS can be between about 3:1 and 1:3. In a particular embodiment, the ratio of PDX to LOS can about 5:5. In another particular embodiment, the ratio of PDX to LOS can be about 8:2.

A therapeutically effective amount of the PDX:LOS combination may be between about 1.0 g/L and 10.0 g/L, administered daily. In another embodiment, a therapeutically effective amount of the PDX:LOS combination may be between about 2.0 g/L and 8.0 g/L, administered daily. In a particular embodiment, a therapeutically effective amount of the PDX:LOS combination may be about 2 g/L of PDX and 2 g/L of LOS, administered daily.

In yet another embodiment of the present invention, PDX is administered in combination with both GOS and LOS. In this embodiment, the PDX:GOS:LOS combination can be administered in a ratio of about 50:33:17. Alternatively, the ratio of the PDX:GOS:LOS combination can be about 1:1:1. In a particular embodiment, the ratio of PDX:GOS:LOS can be about 1:1.5:1.

A therapeutically effective amount of the PDX:GOS:LOS combination may be between about 1.0 g/L and 10.0 g/L, administered daily. In another embodiment, a therapeutically effective amount of the PDX:GOS:LOS combination may be between about 2.0 g/L and 8.0 g/L, administered daily. In an embodiment, a therapeutically effective amount of the PDX:GOS:LOS combination may be about 2 g/L PDX, 2 g/L GOS and 2 g/L LOS, administered daily. In a particular embodiment, a therapeutically effective amount of the PDX:GOS:LOS combination may be about 2 g/L PDX, 1.32 g/L GOS and 2.6 g/L LOS, administered daily. In another embodiment, a therapeutically effective amount of the PDX:GOS:LOS combination may be about 4 g/L PDX, 2.64 g/L GOS and 3.6 g/L LOS, administered daily.

In one embodiment of the invention, PDX can be combined with one or more probiotics and administered to an infant. Any probiotic known in the art will be acceptable in this embodiment. In a particular embodiment, the probiotic is chosen from the group consisting of Bifidobacterium spp. or Lactobacillus spp. In an embodiment, the probiotic is Lactobacillus rhamnosus GG (LGG). In another embodiment, the probiotic is Bifidobacterium lactis. In a specific embodiment, the probiotic is Bifidobacterium lactis Bb-12, available from Chr. Hansen Biosystems, located in Milwaukee, Wis.

In other embodiments of the present invention, the infant formula may contain other active agents such as long chain polyunsaturated fatty acids (LCPUFA). Suitable LCPUFAs include, but are not limited to, α-linoleic acid, γ-linoleic acid, linoleic acid, linolenic acid, eicosapentaenoic acid (EPA), arachidonic (ARA) and docosahexaenoic acid (DHA). In an embodiment, PDX is administered in combination with DHA. In another embodiment, PDX is administered in combination with ARA. In yet another embodiment, PDX is administered in combination with both DHA and ARA. Commercially available infant formula that contains DHA, ARA, or a combination thereof may be supplemented with PDX and used in the present invention. For example, Enfamil® LIPIL®, which contains effective levels of DHA and ARA, is commercially available and may be supplemented with LGG and utilized in the present invention.

In one embodiment, both DHA and ARA are administered in combination with PDX. In this embodiment, the weight ratio of ARA:DHA is typically from about 1:3 to about 9:1. Alternatively, this ratio can be from about 1:2 to about 4:1. In yet another alternative, the ratio can be from about 2:3 to about 2:1. In one particular embodiment the ratio is about 2:1.

The effective amount of DHA in an embodiment of the present invention is typically from about 3 mg per kg of body weight per day to about 150 mg per kg of body weight per day. In one embodiment of the invention, the amount is from about 6 mg per kg of body weight per day to about 100 mg per kg of body weight per day. In another embodiment the amount is from about 10 mg per kg of body weight per day to about 60 mg per kg of body weight per day. In yet another embodiment the amount is from about 15 mg per kg of body weight per day to about 30 mg per kg of body weight per day.

The effective amount of ARA in an embodiment of the present invention is typically from about 5 mg per kg of body weight per day to about 150 mg per kg of body weight per day. In one embodiment of this invention, the amount varies from about 10 mg per kg of body weight per day to about 120 mg per kg of body weight per day. In another embodiment, the amount varies from about 15 mg per kg of body weight per day to about 90 mg per kg of body weight per day. In yet another embodiment, the amount varies from about 20 mg per kg of body weight per day to about 60 mg per kg of body weight per day.

The amount of DHA in infant formulas for use with the present invention typically varies from about 5 mg/100 kcal to about 80 mg/100 kcal. In one embodiment of the present invention it varies from about 10 mg/100 kcal to about 50 mg/100 kcal; and in another embodiment from about 15 mg/100 kcal to about 20 mg/100 kcal. In a particular embodiment of the present invention, the amount of DHA is about 17 mg/100 kcal.

The amount of ARA in infant formulas for use with the present invention typically varies from about 10 mg/100 kcal to about 100 mg/100 kcal. In one embodiment of the present invention, the amount of ARA varies from about 15 mg/100 kcal to about 70 mg/100 kcal. In another embodiment the amount of ARA varies from about 20 mg/100 kcal to about 40 mg/100 kcal. In a particular embodiment of the present invention, the amount of ARA is about 34 mg/100 kcal.

The infant formula supplemented with oils containing DHA and ARA for use with the present invention can be made using standard techniques known in the art. For example, they can be added to the formula by replacing an equivalent amount of an oil, such as high oleic sunflower oil, normally present in the formula. As another example, the oils containing DHA and ARA can be added to the formula by replacing an equivalent amount of the rest of the overall fat blend normally present in the formula without DHA and ARA.

The source of DHA and ARA can be any source known in the art. In an embodiment of the present invention, sources of DHA and ARA are single cell oils as taught in U.S. Pat. Nos. 5,374,567; 5,550,156; and 5,397,591, the disclosures of which are incorporated herein in their entirety by reference. However, the present invention is not limited to only such oils. DHA and ARA can be in natural or refined form.

In one embodiment, the source of DHA and ARA is substantially free of eicosapentaenoic acid (EPA). For example, in one embodiment of the present invention the infant formula contains less than about 16 mg EPA/100 kcal; in another embodiment less than about 10 mg EPA/100 kcal; and in yet another embodiment less than about 5 mg EPA/100 kcal. One particular embodiment contains substantially no EPA. Another embodiment is free of EPA in that even trace amounts of EPA are absent from the formula.

The infant formula of the present invention can be prepared using any method known in the art. In one embodiment, the PDX is provided in powder form. It can be mixed with water and other infant formula ingredients in a mixing tank. If GOS and/or LOS are included in the infant formula, they can be provided in powdered or liquid form. The mixture can then be pasteurized, homogenized and spray-dried to make a finished powder or canned and retorted to make a liquid product.

As an alternative to an infant formula administration, the prebiotic of the present invention can be administered as a supplement not integral to the formula feeding. For example, PDX can be ingested in the form of a pill, tablet, capsule, caplet, powder, liquid or gel. In this embodiment, the PDX can be ingested in combination with other nutrient supplements, such as vitamins, or in combination with a LCPUFA supplement, such as DHA or ARA.

In another embodiment, PDX can be provided in a form suitable for infants selected from the group consisting of follow-on formula, beverage, milk, yogurt, fruit juice, fruit-based drink, chewable tablet, cookie, cracker, or a combination thereof.

In the method of the present invention, the infant is formula-fed. In one embodiment the infant is formula-fed from birth. In another embodiment, the infant is breast-fed from birth until an age which is less than one year, and is formula-fed thereafter, at which time PDX supplementation begins.

Human milk oligosaccharides can increase the population and species of beneficial bacteria in the intestinal tract, have a SCFA profile that is high in acetate and very low in butyrate, and are slowly fermented, avoiding the production of excessive gases. As will be seen in the examples, the administration of PDX, alone or in combination with other prebiotics, can be used to increase the population and species of beneficial bacteria in the intestinal tract, can preferentially shift the SCFA production toward more acetate and propionate production, thereby limiting butyrate production, and can slow down the fermentation rate in the gut so that gas production is limited, minimizing discomfort to the infant. Thus, the administration of PDX, alone or in combination with one or more other prebiotics, can simulate the functional attributes of human milk oligosaccharides in a formula-fed infant.

The following examples describe various embodiments of the present invention. Other embodiments within the scope of the claims herein will be apparent to one skilled in the art from consideration of the specification or practice of the invention as disclosed herein. It is intended that the specification, together with the examples, be considered to be exemplary only, with the scope and spirit of the invention being indicated by the claims which follow the examples. In the examples, all percentages are given on a weight basis unless otherwise indicated.

Example 1

This example illustrates the in vitro fecal fermentation model utilized in the present invention. The fecal fermentation model in vitro mimics the action of the colon microbiota of infants. During fermentation, carbohydrates are consumed and SCFA and gases are produced. After fermentation, an analysis of the effect of the prebiotics on the populations and species of microorganisms present can be accomplished.

The individual carbohydrates which were studied are set forth in Table 1.

TABLE 1 Individual Carbohydrates GOS: Vivinal GOS: Deb. No. 00026961 Borculo Domo Ingredients; received Sep. 17, 2002; purity 95.1% LOS: Morinaga Lactulose Anhydride: MLC-A(F), Lot No. FRDL020926; Morinaga Milk Industry Co. Ltd; received Oct. 4, 2002; purity 97% PDX: Sta-Lite III PDX: Lot No. DZ2K0351913; A. E. Staley FOS: Raftilose P95 Fructo-oligosaccharides: Lot No. PCAB022B02; Raffinerie Notre-Dame/Orafti SA; received Sep. 6, 2002; Purity 95.1% PDX2: Litesse ® Ultra ™ PDX: high molecular-weight polymer, max 22 000 MW; Danisco; Lot No. V36020I INU: Raftiline ® HP: long-chain inulin DP ≧ 23 (Lot no: hptoh11oh1; Orafti B.V.; received October 2002; D.S. 96.9%, Inulin 99.9%, Sucrose + Fructose + Glucose 0.1%).

Fecal samples were collected from healthy infants aged 2.5-13 months. Five experimental groups were run, using different combinations of prebiotic carbohydrates in each fermentation group. Twelve babies were recruited for the Group 1 and 2 fermentations, 17 babies for the Group 3 fermentation, 19 babies for the Group 4 fermentation and 23 babies for the Group 5 fermentation. In groups 1-3, only five babies were able to donate an acceptable sample. The babies recruited for the first fermentation were 4, 4, 4, 6, 6, 6, 8, 8, 9, 9, 9 and 10 months of age, for the second fermentation 3, 4, 6, 6, 6, 7, 8, 9, 10, 10, 12 and 13 months of age, and for the third fermentation 2, 2.5, 3, 4, 4, 4, 4.5, 5, 5, 6, 6, 6, 9, 9, 10, 10 and 11 months of age. The ages of the babies whose samples were used in the fermentation were Group 1: 6, 8, 9, 9, 9 months; Group 2: 4, 8, 10, 12, 13 months; and Group 3: 2.5, 5, 6, 10, 11 months. In the Group 4 fermentation, 10 babies (of which one baby twice) were able to donate an acceptable sample. The donors for the Group 4 fermentation were 2, 2.5, 4, 5, 7, 9, 9, 10, 11 and 15 months of age. For the Group 5 fermentation, twelve babies were able to donate samples, of which the four youngest donors were selected. Thus the donors were 5, 6, 6.5 and 6.5 months of age.

Fecal fermentation in vitro was performed according to the method of Karppinen, which is hereby incorporated by reference in its entirety. Karppinen S., et al., In Vitro Fermentation of Polysaccharides of Rye, Wheat, and Oat Brans and Inulin by Human Faecal Bacteria, J. Sci. Food Agric. 80:1469-76 (2000).

In the present study, 100 mg of carbohydrate samples were weighed into 50 ml bottles and hydrated using 2 ml of carbonate-phosphate buffer at pH 6.9. The samples were kept overnight under anaerobic conditions at 5° C. until preparation of the inoculum. Fecal slurry (12.5%, weight/volume) was prepared under strictly anaerobic conditions in the same buffer by pooling fresh infant feces. Eight ml of the suspension was dosed to the substrate samples and bottles were closed in the anaerobic chamber giving the final fecal slurry concentration of 10% (weight/volume). Samples were incubated at 37° C. for 1, 2, 4, 8 or 24 hours. 0 hour samples were prepared similarly to the centrifugation tubes and frozen rapidly using liquid nitrogen. Fecal blanks without added carbohydrates were included in all fermentation experiments.

Fermentation was finished by removing the bottles from the waterbath and placing them on ice except prior to gas measurement, when samples were kept at room temperature for immediate sampling. Gas volume was measured and gas sample (5 ml) was injected to a nitrogenated headspace bottle. The bottle was placed on ice after the sampling. The fermentation sample was transferred to a centrifugation tube, pH was measured and an aliquot (2 ml) was drawn from the slurry for SCFA analysis and frozen rapidly with liquid nitrogen.

Example 2

This example illustrates the materials and methods necessary to determine the effectiveness of polydextrose as a prebiotic for formula-fed infants. Specifically, this example illustrates the materials and methods necessary to analyze SCFAs and gases.

SCFAs were extracted with diethyl ether and analyzed with gas chromatography as described by Karppinen, et al., which is hereby incorporated by reference in its entirety. Karppinen S., et al., In Vitro Fermentation of Polysaccharides of Rye, Wheat, and Oat Brans and Inulin by Human Faecal Bacteria, J. Sci. Food Agric. 80:1469-76 (2000). Gases (hydrogen, carbon dioxide, methane, hydrogen disulfide, and oxygen as a quality control) were analyzed isothermally at 30° C. using a static headspace technique by gas chromatography according to Karppinen, et al. Id.

Example 3

This example illustrates the effect of PDX on the in vitro SCFA profile produced by the infant colon microbiota. FIGS. 1 and 2 illustrate that the rate of fermentation varies among different prebiotics. The production of total SCFA (a sum of acetic, propionic and butyric acids) is shown in FIG. 1. A decrease in pH, shown in FIG. 2, is also an indication of SCFA production.

As can be seen in the figures, PDX2 is a slowly fermentable carbohydrate, whereas FOS, GOS and LOS were fermented fast and completely. The fermentation rate of PDX2 was comparable to cereal dietary fibers. Not only was PDX2 fermented at the slowest initial rate, but the extent of fermentation was only slightly above the fecal blank. In contrast, the fermentation rate of FOS was so rapid that it was consumed almost completely within the first sampling time points and produced the highest amount of SCFAs among prebiotics tested.

As shown in FIG. 3-5, PDX2 fermentation results in the highest propionate production and the lowest butyrate production after 24 hours. Acetate was still the highest SCFA produced during the fermentation of PDX, although the initial rate was much lower than those of the other substrates. The initial rate of propionate production from PDX2 was similar to that of the other substrates, but higher levels were found at the end of fermentation. In contrast, the fermentation of FOS, GOS and LOS showed increased concentrations of acetate and butyrate and decreased concentration of propionate. As a result, the combined relative proportion of acetate and propionate was much higher for PDX2 than for FOS, LOS or GOS. These results can also be seen in FIG. 6. These results demonstrate that PDX2 was the least butyrate-producing substrate and the only substrate for increasing the relative proportion of propionate.

These results are in agreement with an in vitro study conducted by Wang, X. & Gibson, G. R., Effects of the In Vitro Fermentation of Oligofructose and Inulin by Bacteria Growing in the Human Large Intestine, J. Appl. Bacteriol. 75:373-380 (1993), in which fecal slurry from adult donors was used in the fermentation of various carbohydrates. However, the higher propionate production from PDX in vitro was not shown in vivo in a clinical trial with Chinese adults Jie, Z., et al., Studies on the Effects of Polydextrose Intake on Physiological Functions in Chinese People, Am. J. Clin. Nutr. 72:1503-09 (2000), in which three different PDX concentrations could increase the levels of butyrate and acetate, but not the proportion of propionate. Larger production of butyrate from GOS and FOS has also been shown with human fecal flora associated rats (Djouzi, Z., et al., Compared Effects of Three Oligosacchardies on Metabolism of Intestinal Microflora in Rats Inoculated with a Human Faecal Flora, Br. J. Nutr. 78:313-24 (1997).

Example 4

This example illustrates the effect of combinations of prebiotics on the in vitro fermentation rate by infant colon microbiota. Various combinations of prebiotic carbohydrates were chosen in an attempt to achieve a desirable rate of microbial fermentation in vitro. In this example, the substrate combinations were compared for their fermentation rate (total SCFA production) and changes in pH, shown in FIGS. 7-8.

The addition of PDX to the GOS preparation slowed the fermentation rate of the combination as measured by total SCFA production (FIG. 7). Similarly, the addition of PDX to the LOS preparation slowed the fermentation rate of the combination. The addition of PDX to LOS or GOS also resulted in a more moderate decrease in pH, as shown in FIG. 8. This slower rate of acidification of stool content may lead to less irritation of the intestinal lining or anal region, increasing infant tolerance. The slower decrease in pH by PDX is consistent with slower SCFA production and overall in vitro fermentation rate compared to GOS and LOS. These results demonstrate that PDX can be used to slow down the fermentation rate of the mixtures of PDX and traditional prebiotics such as GOS or LOS.

The effect of the PDX:GOS ratio on the production of total SCFA, acetate, propionate and butyrate was also studied (FIGS. 9-12). FIG. 9 demonstrates that a PDX:GOS ratio of 8:2 led to a slower rate of total SCFA production than did a PDX:GOS ratio of 5:5. FIG. 9 confirms that a PDX:GOS ratio of 8:2 produced less total SCFA than a ratio of 5:5 or 1:9. Thus, these results demonstrate that a higher amount of PDX in the PDX:GOS mixture results in a slower rate of fermentation in vitro. The addition of PDX to GOS also had the tendency to decrease the rate of acetate and butyrate production, but had little impact on the overall rate and final propionate production.

Example 5

This example illustrates the effect of PDX on in vitro gas production by infant colon microbiota. Total gas production, measured as the total volume per fermentation bottle, was about equal with GOS, LOS and FOS, shown in FIG. 13. In contrast, PDX results in lower overall gas production during fermentation by infant fecal bacterial microbiota. The lower overall gas production seen in PDX also indicates that it is fermented more slowly than the other prebiotics studied.

In addition to total gas production, carbon dioxide production is an important measure of infant tolerance to dietary prebiotics. The major gas product of all prebiotics tested was carbon dioxide. It was produced in 3- and 44-76-fold higher amounts than hydrogen or hydrogen disulphide, respectively.

Overall, production of carbon dioxide was the lowest for PDX when compared with FOS, GOS and LOS (FIG. 14). Carbon dioxide was the main gas produced during the fermentation of FOS, GOS and LOS, showing maximum levels between 320-380 μmol. In contrast, PDX showed much lower levels of carbon dioxide formation (200 μmol). Hydrogen formation from PDX by infant fecal microbiota was lower (about one third) than carbon dioxide production, and considerably lower than levels of hydrogen produced from FOS, GOS and LOS (FIG. 15). Hydrogen disulphide formation from PDX was 1:44 compared to the formation of carbon dioxide and maximal hydrogen disulphide production was at about the same level of concentration for all test prebiotics (FIG. 16). The larger proportion of carbon dioxide formation compared to the formation of hydrogen (1000-fold) and methane (10-fold) was also shown by Wang and Gibson. Wang, X. & Gibson, G. R., Effects of the In Vitro Fermentation of Oligofructose and Inulin by Bacteria Growing in the Human Large Intestine, J. Appl. Bacteriol. 75:373-380 (1993). Since methanogenesis was not observed in the present study, hydrogen disulphide was formed presumably from primary hydrogen. Levitt, et al., Gas Metabolism in the Large Intestine, CRC Press, Boca Raton 131-154 (1995). It is possible that hydrogen was not detected due to its further metabolism to secondary gas, hydrogen disulphide, at late time points.

Example 6

This example illustrates the materials and methods necessary to determine the effect of PDX on the population and species of microbiota from the infant colon. Briefly, the example utilizes an infant gut model to evaluate certain prebiotic compounds. The infant gut in vitro model utilized, which was based on an adult model, was comprised of two 100 ml glass vessels, arranged in series to represent the proximal and distal regions of the infant colon. The feed flow was controlled at a rate that took into account the shorter passage time in the infant gut, as compared to an adult gut. To model in vivo differences in pH within the colon, vessel 1 (V1) was controlled at pH 5.2 and vessel 2 (V2) was controlled at pH 6.7. Temperature was controlled at 37° C. by a circulating water bath. The feed and culture vessels were magnetically stirred and maintained under an anaerobic atmosphere by inflowing oxygen-free nitrogen (15 mL/min).

Once the system was inoculated with infant fecal slurry, the two fermenter vessels were left for up to 24 hours in batch mode. This allowed the bacterial populations to equilibrate in their new environment and increase in density. The feed flow was then turned on and the fermenter ran in continuous culture mode for the remainder of the experiment. The feed flow rate was controlled at 11.11 ml/h. In this study, the fermenters were run for 12 days, 6 days being fed Enfalac infant formula (Mead Johnson Nutritionals, Evansville, Ind.) and a further 6 days being fed Enfalac and the added prebiotic or prebiotic combination.

Samples of 5 ml were then taken aseptically from V1 and V2 and prepared for the culture independent microbial enumeration procedure Fluorescence In Situ Hybridisation (FISH) and microscopy for the identification and enumeration of specific bacterial species. Using FISH allows the accurate determination of the effect of prebiotics on specific bacterial populations in the proximal and distal regions of the infant colon.

Prebiotics were added to the feed individually or in combinations, at a total concentration of 7.5 g/l (0.75% w/v). The following oligosaccharides were used:

TABLE 2 Prebiotics Tested Prebiotic Type Manufacturer Lactulose (LOS) Syrup Morinaga Milk Ind. Co. Ltd., Japan Galacto-oligosaccharide E0002 Supplied by Mead (GOS) powder Johnson Polydextrose (PDX) ‘Litesse Danisco Ultra’ powder Fructo-oligosaccharide Raftilose ® Orafti P95 powder

The infant donors were carefully selected and ideally aged 2-4 months, formula-fed (exclusively where possible), healthy and not under recent antibiotic treatment. A minimum age of 2 months was preferred as the infant gut microbiota is established by this age.

TABLE 3 Donor Information Donor Fermentation Code Age Feed Run KB 16 weeks SMA Gold F1 JS 13 weeks Cow & Gate F2 F 19 weeks SMA Gold and breast-fed F3 AE 9½ weeks breast fed F4 AE 14 weeks breast fed F5

The microbial flora of the infant gut for fermentation tests was provided by freshly voided infant feces. A fecal sample of at least 3.5 g was usually required. The fecal sample was retained in the diaper which, immediately on removal from the infant, was placed by the caregiver into an anaerobic jar with an opened anaerobic gas pack. This was collected and processed as soon as possible (usually within the hour).

In the laboratory, the feces were removed from the diaper and weighed. A 10% (w/v) fecal slurry was prepared by homogenizing the samples in anoxic and pre-warmed (overnight in the anaerobic cabinet) 1×PBS solution, using a stomacher at medium rate for 120 seconds.

Each of the fermenter vessels was inoculated with 5 ml of the 10% w/v fecal suspension. An aliquot of the fecal suspension (sample S) was also taken for analysis

A 375 μl sample of the fecal suspension (sample S) or of each fermenter sample was required in duplicate for bacterial counts by FISH. Each sample was fixed by mixing thoroughly in 1.125 ml cold, filtered 4% (w/v) paraformaldehyde solution in PBS pH7.2) and storing at 4° C. overnight (or at least 4 hours).

The fixed sample was centrifuged at 13,000×g for 5 minutes and the supernatant discarded. The pellet was washed twice by re-suspending in 1 ml of cold, filtered 1×PBS, each time pelleting the cells by centrifugation and discarding the supernatant. The pellet was finally re-suspended thoroughly in 150 μl of filtered PBS; 150 μl of 96% (v/v) ethanol is then mixed in well. The cell preparation was then stored at −20° C. for at least 1 h before further processing.

In the hybridization step, 16 μl of the cell preparation (brought to ambient temperature) was mixed with 200 μl filtered, pre-warmed 2× hybridization buffer (30.3 mM Tris-HCl pH 7.2, 1.4 mM NaCl) containing 15.1 ml/l 10% (w/v) SDS. This mixture was warmed to the appropriate hybridization temperature and then mixed with the probe (50 ng/μl) in the ratio 9:1, respectively. The hybridization preparation was then returned to the hybridization oven to incubate overnight.

Finally, the hybridized cell preparations were collected onto 0.2 μm filters for microscopic observation. Depending upon the cell density, between 5 μl and 100 μl of the cell preparation was added to filtered, pre-warmed (to hybridization temperature) washing buffer (5-7 ml 20 mM Tris-HCl pH 7.2, 0.9 M NaCl). 20 μl DAPI (4′,6-diamidino-2-phenylindole) was also added to the mixture to stain all cells and obtain total cell counts for each sample. This was then vacuum-filtered onto a 0.2 m polycarbonate filter and placed on a microscope slide. To minimize fading of the fluorescent dye, a drop of SlowFade™ (Molecular Probes) was placed on the filter and covered with a cover slip; the slides were then stored in the dark at 4° C. until used. Bacteria tagged with a Cy3 fluorescent probe were counted using fluorescence microscopy (Leitz, Wetzlar, Germany) at 550 nm; UV light was used for counting DAPI stained bacteria. Bacteria were counted in at least 15 fields taken at random and the average of these used to estimate the number of cells per ml of the original sample.

Four comparison, fermentation tests were run as listed below.

TABLE 4 Fermentation Runs Fermentation Run Test Substances F1 FOS F2 Human Milk PDX F3 GOS F4 1:1 LOS:GOS 1:1 PDX:LOS F5 LOS 1:1 PDX:GOS

Example 7

This example illustrates the effect of PDX on the population and species of bacteria in the infant gut. In fermentation run 1 (F1), FOS was added to the formula feed and run in a fermenter system. FOS, which has traditionally been considered a good prebiotic ingredient, resulted in increases in Bifidobacteria and Clostridia and decreases in Lactobacilli and Bacteroides in V1. The addition of FOS to formula feed resulted in no change in Bifidobacteria and Lactobacilli levels and increases in Clostridia and Bacteroides in V2.

In F2, PDX and human milk were run in parallel fermenter systems. Human milk samples were provided by a maternity ward and stored frozen. These were early milk samples of varying volumes from several donors. The human milk feed was run without dilution or addition of lactose in order to maintain comparable levels of oligosaccharides and other nutrients. There was insufficient human milk to run this fermenter for 12 days, in parallel with the PDX fermenter. More frequent samples were therefore taken, at days 0, 4, 6 and 8. For comparative purposes, additional samples were taken from the PDX fermenter at day 8, and also at day 11.

As would be expected, human milk promoted good growth of beneficial bacteria, both Bifidobacteria and Lactobacilli, and decreased Clostridia levels, as shown in FIG. 17. Bifidobacteria and Lactobacilli clearly increased in population in both vessels. Bacteroides numbers remained at a similar level throughout the fermentation.

The results of PDX addition to the formula feed were also favorable, with a marked increase in Lactobacilli and decreases in both Clostridia and Bacteroides in both vessels (FIG. 17).

In F3, GOS was added to the formula feed and run in a fermenter system. The addition of GOS to the formula feed had little apparent effect on Lactobacilli in either vessel, but increased Bifidobacteria in V1 and V2, and decreased Clostridia and Bacteroides in V1 but not V2.

The combination of LOS:GOS (1:1) was run against 1:1 PDX:LOS in a parallel fermenter system during F4. The LOS:GOS combination was effective in increasing numbers of Lactobacilli in both vessels and Bifidobacteria in V1, and in decreasing Bacteroides in V1. Clostridia decreased in V2 but increased in V1.

Supplementation of the formula feed with a 1:1 combination of PDX:LOS resulted in an increase in Lactobacilli in V1, but a slight decrease in Bifidobacteria in each vessel. Clostridia tended to decrease in both vessels which Bacteroides decreased mainly in V2.

In F5, LOS was supplemented into the formula feed and run in a parallel fermenter system against a 1:1 combination of PDX and GOS. The addition of LOS to the formula feed increased Lactobacilli in both vessels. However, Clostridia also increased in V2 and Bifidobacteria decreased in both vessels. Although Bacteroides decreased in V1 this was not maintained in V2. The addition of PDX:GOS to the formula feed increased levels of Bifidobacteria and Lactobacilli in both vessels, but also caused Clostridia levels to increase. Bacteroides levels increased in V2 only.

Overall, Bifidobacteria increased in proportion to the total bacterial population in V1 with human milk, GOS, FOS, PDX and the PDX:GOS combination. In V2, GOS, the PDX:GOS combination and the LOS:GOS combination led to an increase in Bifidobacteria. Clostridia decreased in proportion to the total population in V1 with human milk, GOS and PDX, and decreased in V2 with human milk, PDX and the LOS:GOS combination.

In V1, the Lactobacilli showed an increase following supplementation with LOS, PDX, human milk or PDX combinations, whereas increases in Lactobacilli were observed in V2 with LOS, PDX, human milk, and GOS combinations. The increases in the percentage of Lactobacilli were particularly marked with PDX and the PDX:GOS combination and the LOS:GOS combination in V2.

Overall, PDX was effective in increasing Lactobacilli and decreasing levels of Clostridia and Bacteroides, with only slight increases in Bifidobacteria in V1. The PDX:GOS combination also looked favorable for Bifidobacteria, which increased amongst the total bacteria (although not as a percentage of the four groups) and increased Lactobacilli at a pH of 5.2, but it also had the unfavorable effect of increasing Bacteroides numbers.

When human milk was tested in the model system designed by the inventors, Bifidobacteria and Lactobacilli levels increased in number, while Clostridia decreased in number. This effect was most consistently duplicated with PDX, and with GOS, either alone or in combination with LOS or PDX. FOS, which is another carbohydrate that is currently utilized in various infant formulas, was tested and did not produce the same desirable results.

Example 8

This example illustrates one embodiment of an infant formula of the present invention.

TABLE 5 Nutrient Information for Infant formula Ingredient Per 10,000 L Demineralized Whey Solids 534.337 kg Fat Blend 339.695 kg Nonfat Milk Solids 191.234 kg Lactose 136.321 kg Galactooligosaccharide Syrup Solid 35.096 kg Polydextrose 22.222 kg Potassium Citrate 7.797 kg Mono- and Diglycerides 7.233 kg Single Cell Arachidonic Acid Oil 6.486 kg Calcium Phosphate, Tribasic 4.185 kg Ascorbic Acid 1,403.323 g Sodium Ascorbate 1,168.402 g Inositol 407.029 g Taurine 402.962 g Corn Syrup Solids 188.300 g Niacimamide 89.857 g Calcium Pantothenate 42.443 g Vitamin B₁₂ 23.613 g Biotin Trituration 23.613 g Thiamin HCl 8.022 g Pyridoxine HCl 6.176 g Folic Acid 2.260 g Lecithin Concentrate 3.694 kg Single Cell Docosahexaenoic Acid Oil 3.243 kg Carrageenan 2.826 kg Calcium Chloride 2.650 kg Sodium Chloride 1.410 kg Maltodextrin 484.199 g CMP, free acid 151.951 g AMP, free acid 33.944 g GMP, disodium salt 18.347 g UMP, disodium salt 7.559 g Ferrous Sulfate 0.620 kg Sodium Citrate 0.455 kg Tocopheryl Acetate, DL-Alpha 160.882 g Soy Oil 139.612 g Vitamin A Palmitate 17.253 g Cholecalciferol Concentrate 5.715 g Vitamin K, Liquid Phytonadione 0.538 g Zinc Sulfate 214.225 g Sodium Selenite 51.112 g Cupric Sulfate 22.885 g Lactose 12.659 g Manganese Sulfate 3.119 g Water, Deflouridated 10,311.900 kg

LOS is generated when lactose is heated at a high temperature. Therefore, in this embodiment the product contains indigenous LOS. The level of indigenous LOS in the product is approximately 2 g/L.

Example 9

This example illustrates another embodiment of an infant formula of the present invention.

TABLE 6 Nutrient Information for Infant formula Ingredient Per 10,000 L Demineralized Whey Solids 534.337 kg Fat Blend 339.695 kg Nonfat Milk Solids 191.234 kg Lactose 142.000 kg Galactooligosaccharide Syrup Solid 23.164 kg Polydextrose 22.222 kg Lactulose Syrup Solid 10.353 kg Potassium Citrate 7.797 kg Mono- and Diglycerides 7.233 kg Single Cell Arachidonic Acid Oil 6.486 kg Calcium Phosphate, Tribasic 4.185 kg Ascorbic Acid 1,403.323 g Sodium Ascorbate 1,168.402 g Inositol 407.029 g Taurine 402.962 g Corn Syrup Solids 188.300 g Niacimamide 89.857 g Calcium Pantothenate 42.443 g Vitamin B₁₂ 23.613 g Biotin Trituration 23.613 g Thiamin HCl 8.022 g Pyridoxine HCl 6.176 g Folic Acid 2.260 g Lecithin Concentrate 3.694 kg Single Cell Docosahexaenoic Acid Oil 3.243 kg Carrageenan 2.826 kg Calcium Chloride 2.650 kg Sodium Chloride 1.410 kg Maltodextrin 484.199 g CMP, free acid 151.951 g AMP, free acid 33.944 g GMP, disodium salt 18.347 g UMP, disodium salt 7.559 g Ferrous Sulfate 0.620 kg Sodium Citrate 0.455 kg Tocopheryl Acetate, DL-Alpha 160.882 g Soy Oil 139.612 g Vitamin A Palmitate 17.253 g Cholecalciferol Concentrate 5.715 g Vitamin K, Liquid Phytonadione 0.538 g Zinc Sulfate 214.225 g Sodium Selenite 51.112 g Cupric Sulfate 22.885 g Lactose 12.659 g Manganese Sulfate 3.119 g Water, Deflouridated 10,311.900 kg

LOS is generated when lactose is heated at a high temperature. Therefore, in this embodiment the product contains both added and indigenous LOS. The total level of LOS in the product, including both added and indigenous LOS, is approximately 2.6 g/L.

Example 10

This example illustrates yet another embodiment of an infant formula of the present invention.

TABLE 7 Nutrient Information for Infant formula Ingredient Per 10,000 L Demineralized Whey Solids 534.337 kg Fat Blend 339.695 kg Nonfat Milk Solids 191.234 kg Lactose 119.321 kg Galactooligosaccharide Syrup Solid 46.327 kg Polydextrose 44.444 kg Lactulose Syrup Solid 20.706 kg Potassium Citrate 7.797 kg Mono- and Diglycerides 7.233 kg Single Cell Arachidonic Acid Oil 6.486 kg Calcium Phosphate, Tribasic 4.185 kg Ascorbic Acid 1,403.323 g Sodium Ascorbate 1,168.402 g Inositol 407.029 g Taurine 402.962 g Corn Syrup Solids 188.300 g Niacimamide 89.857 g Calcium Pantothenate 42.443 g Vitamin B₁₂ 23.613 g Biotin Trituration 23.613 g Thiamin HCl 8.022 g Pyridoxine HCl 6.176 g Folic Acid 2.260 g Lecithin Concentrate 3.694 kg Single Cell Docosahexaenoic Acid Oil 3.243 kg Carrageenan 2.826 kg Calcium Chloride 2.650 kg Sodium Chloride 1.410 kg Maltodextrin 484.199 g CMP, free acid 151.951 g AMP, free acid 33.944 g GMP, disodium salt 18.347 g UMP, disodium salt 7.559 g Ferrous Sulfate 0.620 kg Sodium Citrate 0.455 kg Tocopheryl Acetate, DL-Alpha 160.882 g Soy Oil 139.612 g Vitamin A Palmitate 17.253 g Cholecalciferol Concentrate 5.715 g Vitamin K, Liquid Phytonadione 0.538 g Zinc Sulfate 214.225 g Sodium Selenite 51.112 g Cupric Sulfate 22.885 g Lactose 12.659 g Manganese Sulfate 3.119 g Water, Deflouridated 10,325.600 kg

LOS is generated when lactose is heated at a high temperature. Therefore, in this embodiment the product contains both added and indigenous LOS. The total level of LOS in the product, including both added and indigenous LOS, is approximately 3.6 g/L.

All references cited in this specification, including without limitation, all papers, publications, patents, patent applications, presentations, texts, reports, manuscripts, brochures, books, internet postings, journal articles, periodicals, and the like, are hereby incorporated by reference into this specification in their entireties. The discussion of the references herein is intended merely to summarize the assertions made by their authors and no admission is made that any reference constitutes prior art. Applicants reserve the right to challenge the accuracy and pertinence of the cited references

These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein. 

1. An infant formula comprising a prebiotic composition comprising a) a first prebiotic having a rate of fermentation in the intestinal tract that is slower than galacto-oligosaccharide and which comprises polydextrose and b) a second prebiotic which comprises a prebiotic selected from the group consisting of galacto-oligosaccharide, lactulose, and combinations thereof, wherein the prebiotic composition is present at a level of between about 2.0 g/L and about 8.0 g/L, and the ratio of the first prebiotic to the second prebiotic is between about 1:3 and about 3:1.
 2. The infant formula according to claim 1, comprising polydextrose and galacto-oligosaccharide.
 3. The infant formula according to claim 1, comprising polydextrose and lactulose.
 4. The infant formula according to claim 1, comprising polydextrose, galacto-oligosaccharide and lactulose.
 5. The infant formula according to claim 1, which further comprises a. a lipid or fat; b. a protein source selected from the group consisting of whey protein, casein, casein protein, nonfat milk, hydrolyzed protein and combinations thereof; and c. about 5 to about 200 mg/100 kcal of a source of long chain polyunsaturated fatty acids.
 6. The infant formula according to claim 5, wherein the source of long chain polyunsaturated fatty acids comprises docosahexanoic acid, arachidonic acid or combinations thereof.
 7. The infant formula according to claim 6, wherein the source of long chain polyunsaturated fatty acids comprises docosahexanoic acid and arachidonic acid, further wherein the ratio of arachidonic acid to docosahexanoic acid is from about 1:3 to about 9:1.
 8. The infant formula according to claim 5, wherein the lipid or fat is present at a level of about 3 to about 7 g/100 kcal.
 9. The infant formula according to claim 5, wherein the protein source is present at a level of about 1 to about 5 g/100 kcal.
 10. The infant formula according to claim 5, which further comprises at least one probiotic.
 11. The infant formula according to claim 10, wherein the probiotic is selected from the group consisting of Bifidobacteria spp., Lactobacillus spp and combinations thereof.
 12. The infant formula according to claim 1, wherein the second prebiotic further comprises fructo-oligosaccharide, inulin, gluco-oligosaccharide, isomalto-oligosaccharide, xylo-oligosaccharide, soybean oligosaccharide, chito-oligosaccharide, gentio-oligosaccharide, manno-oligosaccharide, lactosucrose, raffinose, aribino-oligosaccharide, glucans, siallyl and fuco-oligosaccharide, or combinations thereof.
 13. An infant formula comprising a first prebiotic having a rate of fermentation slower than galacto-oligosaccharide that comprises polydextrose and a second prebiotic that comprises a combination of galacto-oligosaccharide and lactulose, wherein the amount of polydextrose present in the infant formula is about 2.0 g/L, the amount of galacto-oligosaccharide present in the infant formula is about 2.0 g/L and the amount of lactulose present in the infant formula is about 2.0 g/L.
 14. An infant formula comprising a first prebiotic having a rate of fermentation slower than galacto-oligosaccharide that comprises polydextrose and a second prebiotic that comprises a combination of galacto-oligosaccharide and lactulose, wherein the amount of polydextrose present in the infant formula is about 2.0 g/L, the amount of galacto-oligosaccharide present in the infant formula is about 1.32 g/L and the amount of lactulose present in the infant formula is about 2.6 g/L.
 15. An infant formula comprising a first prebiotic having a rate of fermentation slower than galacto-oligosaccharide that comprises polydextrose and a second prebiotic that comprises a combination of galacto-oligosaccharide and lactulose wherein the amount of polydextrose present in the infant formula is about 4.0 g/L, the amount of galacto-oligosaccharide present in the infant formula is about 2.64 g/L and the amount of lactulose present in the infant formula is about 3.6 g/L. 